Aeronautical propeller



E. GEIL ET AL AERONAUTIGAL PROPELLER Filed July 23, 1934 July 7, 1936 Patented July 7, 1936 UNITED STATES PATENT OFFICE AERONAUTICAL PROPELLER New York Application July 23, 1934, Serial No. 736,580 In Germany July 25, 1933 9 Claims. (CL I'M-P159) Our invention relates to hubs of aeronautical propellers especially when made of solid metal the blades are now made from light metal alloys with a high magnesium content.

It has been found that between the hub of the propellers which are usually constructed of steel and the blades consisting of magnesium-containing alloys, there is danger of electrolytic corrosion due to the fact that there is an essential potential difference between the two metals. This corrosion sometimes causes a loss in the tensile strength of the propeller to such a degree that breakages occur.

The object of the invention is to prevent electrolytic corrosion between the metal of the hub and the metal of the blades. A further object is to damp the strong continuous vibration at the fixing point; Another object of the invention is to provide means for attaching the hub to the shaft of the propeller which will ensure continuous, reliable running. To this end an intermediate layer of electric isolating material is provided between the shaft of the blades and the hub. Other objects of the invention will appear as the device is described in detail.

In the accompanying drawing Figure 1 is a section of the propeller shaft and hub and Figure 2 is a section through another shaft and hub where the propeller is adjustable during flight.

In this drawing we have illustrated two embodiments of the invention and have shown the same as designed primarily for use, but it will be understood that the invention may take various forms and that it may be utilized for various purposes.

In these embodiments of the invention here 1 shown the shaft of thepropellers is shown under I. This shaft is cylindrical and consists of a magnesium alloy of high magnesium content. The end of the shaft is attached in the usual manner to the two-part hub 2 consisting of steel. The details of this hub are not shown since they are known to the man skilled in the art. The fixing of the shaft is effected by clamping ring 3. Between the cylindrical part of the shaft of the propeller and the hub there is an interme-.

diate layer 4 of an isolating material. This electric isolating material may be mica, cellulose or rubber, etc., but this intermediate layer is preferably made of fibre since fibre is elastic per se and capable of absorbing the elastic vibrations so that the surface of the shaft of the propeller is not worn or damaged.

As it clearly appears from both Figs. 1 and 2, it is not necessary that the propeller shank should be completely isolated electrically from the hub, but generally it is suflicient to provide said insulation at joints where in consequence of great 5 mechanical stresses the results of electrolytical or frictional corrosion would be especially disastrous.

In Figure 2 the shaft l of the propeller is again attached in hub 2. In this case the intermediate layer is conical and attached at the fixing point by cap screw 5.

It has been found that sometimes when running damages occur to the surface of the propeller shaft which cause a breakage of the propeller blade. The inventors have found out that these damages are due to electrical corrosion in combination with the continuous vibration at the fixing point. The intermediate layer of electric isolating material or of a material with another electric potential, especially if the isolating material is elastic per se, hinders these damages as the electrolytic corrosion cannot occur and the elastic material absorbs the vibrations.

Having now fully described our invention, what we claim as new and desire to secure by Letters Patent isz- 1. In an aeronautical propeller, the combination which comprises a steel hub, a magnesiumcontaining propeller blade having its shank rigidly seated in said hub, and a resilient isolating member positioned between a terminal portion of said hub and an intermediate portion of said shank which is exposed to severe bending stresses, said member being adapted to prevent direct contact, frictional displacement and corrosion of said portions of the shank and of the hub and to convert frictional displacements into molecular displacements within the body of said member.

2. In an aeronautical propeller, the combina- 40 tion which comprises a steel hub, a propeller blade constituted of a magnesium-containing metal having its shank rigidlyfixed in said hub, and an elastic isolating member positioned between said hub and a portion of said shank which is exposed to severe bending stresses, said member being adapted to prevent direct contact, frictional displacement and corrosion of said portions of the shank and of the hub and to convert frictional displacement into displacement within the body of said member.

3. In an aeronautical propeller, the combination which comprises a steel hub, an internal seat in said hub, a propeller blade made of a mag-. nesium alloy mounted in said hub, a shank integral with said blade having an end rigidly fixed in said internal seat, an isolating member of resilient character seated between said hub. and said shank preventing direct contact of the terminal portion of said hub with the portion of the shank which is exposed to severe bending stresses, and means for exerting substantial pressure between said isolating member and of said shank to prevent frictional displacements in said surface caused by vibrations of said shank and to damp such vibrations.

4. In an aeronautical propeller, the combination which comprises a steel hub, an internal seat of annular character in said hub, a propeller blade having a cylindrical shank and made of a magnesium alloy mounted in said hub, an end on said shank rigidly fixed in said internal seat, an isolating member constituted of a resilient material seated between said hub and said shank to prevent direct contact thereof at the portion of the shank exposed to severe bending stresses and to breakage, and means for tightly pressing together the. surfaces of contact of said shank of said isolating member and of said hub to prevent frictional displacements in said surfaces caused by vibrations of said shank and to convert such displacements into displacements within said isolating member.

5. In an aeronautical propeller, the combination which comprises a steel hub, an internal seat in said hub, a shank made of a magnesium alloy mounted in said hub, an end on said shank rigidly fixed in said internal seat, an elastic isolating member inserted in between said hub and said shank to prevent direct contact thereof at the portion of the shank which is exposed to severe bending stresses, and a clamping ring for said hub capable of tightly pressing together the surfaces of contact of said shank, of said isolating member and of said hub to prevent frictional displacements in said surfaces caused by vibrations of said shank and to convert such displacements into displacements within said isolating member.

6. In an aeronautical propeller, the combination which comprises a steel hub, an internal seat in said hub, a shank made of a magnesium and the portion of the shank principally exposed to bending stresses having snugly fitting contact surfaces co-operating with corresponding surfaces of said hub and of said shank, and means for tightly pressing together said contact sur- 5 faces to prevent frictional displacements in said surfaces caused by vibrations of said shank and to convert such displacements into displacements within said spacing means.

'7. In an aeronautical propeller, the combination which comprises a steel hub, an internal seat in said hub, a shank made of a magnesium alloy mounted in said hub, an end on said shank rigidly fixed in said internal seat, an annular spacing member of resilient character seated between and having snugly fitted surfaces cooperating with said shank and said hub at the terminal region thereof, and means for maintaining said co-operating surfaces under substantial pressure to prevent frictional displacements in said surfaces by converting such displacements into displacements within said spacing member.

8. In an aeronautical propeller, the combination which comprises a steel hub, an internal seat in said hub, a shank made of a light metal alloy mounted in said hub, an end of said shank rigidly fixed in said internal seat, an annular isolating member of resilient character seated between an intermediate portion of said shank and said hub and having snugly fitted surfaces co-operating therewith, and means for applying pressure substantially vertically to said co-operating surfaces to convert frictional displacements in said surfaces into displacements in the body of said isolating member.

9. In an earonautical propeller, the combination which comprises a steel hub, an internal seat in said hub, an end on said shank rigidly fixed in said internal seat, a resilient, annular isolating member having a conical face seated between said shank and said hub at the terminal region thereof and having snugly fitting surfaces co-operating with corresponding surfaces of said shank and of said hub, and means for applying pressure to said co-operating surfaces to convert frictional displacements into displacements in the body of said isolating member.

ERICH GEIL. HEINRICH EBERT. 5 

